1. Field of the Invention
The present invention generally relates to diagnostic instruments such as hematology analyzers, blood chemistry analyzers and other instruments that determine certain physiological properties of patients, and more specifically relates to blood and serum sample metering devices used in such diagnostic instruments. Even more particularly, the present invention relates to a proboscis used in the sample metering devices of such diagnostic instruments.
2. Description of the Prior Art
Many diagnostic instruments, such as hematology analyzers and wet and dry blood chemistry analyzers, employ a sample metering device which is engineered to aspirate and dispense precise minute volumes of a fluid. The metering device often includes a metering probe, or proboscis, on which is removably fitted a disposable plastic tip.
FIGS. 1-3 illustrate one form of a conventional proboscis 2 used in a dry chemistry analyzer. The proboscis 2 has formed therein a lumen 4 of constant diameter extending axially therethrough from its proximal end 6, where it is coupled to a metering pump forming part of the overall sample metering device of the diagnostic equipment, to its distal free end 8, which has a relatively small orifice 10 through which the lumen 4 is in fluid communication with the disposable tip situated on the distal end 8 of the proboscis 2. The metering pump creates a partial vacuum or partial pressure within the proboscis lumen 4, and concomitantly within the disposable tip, to selectively draw into the tip or dispense therefrom a specific amount of a sample liquid, such as blood, serum, a chemical reagent or the like. The disposable plastic tip mounted on the distal end portion 8 of the proboscis 2 is removed therefrom and properly discarded after the sample metering operation has been completed.
The diagnostic instrument handles sample fluids (blood, serum, chemical reagents or the like) which by their very nature can be sticky substances that can, over time, coagulate or adhere to surfaces they contact. The blood sample, serum, chemical reagent or other sticky substance may splash onto the distal end 8 of the proboscis 2 when the sample liquid is being aspirated, or perhaps when there is a bubble in the aspirated or expelled sample fluid which bursts, or if the proboscis 2 is not moved smoothly by the sample metering device in either an axial direction or a lateral direction. The fluid held by the disposable tip may enter the lumen 4 or coat the lumen orifice 10 and clog or constrict the orifice or lumen, thereby possibly affecting the accuracy of any metering operation performed by the diagnostic instrument or rendering the instrument inoperable.